I was asking myself the same question after the UK election. I know for sure that the German SPD is almost dead. Gerhard Schröder was to the SPD what George W. Bush was to the GOP. And Tony Blair also hurt Labour in the U.K.
The "fall" of the SPD in recent elections can be explained more by Merkel's stranglehold occupation on the centre ground - easy to do when you are as ideology-less as her - than by the general decline of Social Democrats in Europe. The latter is obviously a factor as well, but the huge losses since 2005, especially when compared to the CDU, are more related to Merkel than to anything else.
